Catalyst for oxacylation and use of the same

ABSTRACT

This invention relates to a catalyst which comprises palladium metal as the main catalyst, tin metal or a mixture of tin and additional metals as the promoter, in combination with an alkali or alkaline earth metal compound, supported on the outer surface of a porous carrier. The catalyst is used in the process for producing allyl acetate through the oxacylation of propylene, acetic acid and oxygen in a vapor phase. The catalyst of the present invention exhibits high catalytic activity, high catalytic selectivity and high catalytic life, which greatly increases the economic utility of the oxacylation process.

FIELD OF THE INVENTION

[0001] This invention relates to a catalyst which is comprised ofpalladium metal as the main catalyst, tin metal or a mixture of tin andadditional metal(s) as the promoter, in combination with an alkali oralkaline earth metal compound, supported on the outer surface of aporous carrier. The catalyst is used in the process for producing allylacetate through the oxacylation of propylene, acetic acid and oxygen ina vapor phase.

BACKGROUND OF THE INVENTION

[0002] Previously, in the production of allyl acetate through theoxacylation of propylene, acetic acid and oxygen in a vapor phase, asilica carrier impregnated with palladium only was the main catalyst,and alkali or alkaline earth metal compound was used as the activator(U.S. Pat. No. 3,925,452). In order to get better activity from thiscatalyst, the oxacylation should be performed at higher temperatures.Under these conditions, the formation of carbon dioxide byproduct wasincreased, and the space time yield (STY, the yield per hour per literof the catalyst) of allyl acetate was unable to be promoted even byincreasing the amounts of palladium or the activator. Generally, by onlyusing palladium as the catalyst during the oxacylation process, thespace time yield of allyl acetate would not exceed 60 (g/hr/l ofcatalyst), and the selectivity of such a catalyst to allyl acetate wouldonly reach 87%. In other words, most of propylene reactant was burnedinto carbon dioxide or converted into other byproducts. Apparently, whenonly palladium and the activator were used as the catalyst, thecatalytic ability of the catalyst was rather low, and waste resultedfrom the complete burning of propylene into carbon dioxide, whichadversely influenced the industrial process.

[0003] In order to improve on this drawback, in the preparation processof the catalyst for oxacylation reaction, other metals were added so asto increase the activity and selectivity of the catalyst (U.S. Pat. No.3,917,676). Therefore, most of the compositions of the catalysts werecomprised of, not only palladium, the main catalyst, and alkali oralkaline earth metal, the activator, but also other metals, as thepromoters. For example, along with catalysts with the combination of themain catalyst palladium and the promoters of potassium, bismuth andbarium (U.S. Pat. No. 4,571,431), the combination of the main catalystpalladium and the promoters of copper, lead, ruthenium and rhenium (EP0361484), etc. have been disclosed. Among these, a catalyst with thecombination of the main catalyst palladium and the promoter copperexhibited higher activity and selectivity (U.S. Pat. No. 5,011,980).

[0004] For the purpose of high catalytic activity and high catalystselectivity, besides the addition of other metals as the promoter inpreparing the catalyst, a certain amount of water as a diluent should beadded into the feeding materials of propylene, acetic acid and oxygenfor performing the oxacylation reaction, in the traditional process ofproducing ally acetate. If moisture content was under a certain ratio,the catalytic activity and life of the catalyst could not be retainedand would deteriorate rapidly. Usually, the addition of the waterdiluent would limit the yield of the final product. Further, the finalproduct, allyl acetate, should be purified after the oxacylation, whichwould result in consuming and wasting energy of the whole process, andthe economical effect could not be attained.

[0005] In the presence of the catalyst produced in this invention, whileno water is added into the reactant materials for the oxacylationprocess, or only a small amount of water is added in accordance with therequirement of the process, not only will the catalytic activity andlife of the catalyst be retained and not deteriorate, but a highcatalytic activity and high selectivity will be attained. Therefore, theenergy consumed and wasted resulting from the addition of water can beavoided, and the economical effect of the oxacylation process can begreatly increased.

SUMMARY OF THE INVENTION

[0006] This invention relates to a catalyst which is comprised ofpalladium metal as the main catalyst, tin metal or a mixture of tin andadditional metal(s) as the promoter, in combination with an alkali oralkaline earth metal compound, supported on the outer surface of aporous carrier. The catalyst is used in the process for producing allylacetate through the oxacylation of propylene, acetic acid and oxygen ina vapor phase. The catalyst of the present invention exhibits highcatalytic activity, high catalytic selectivity and high catalytic life,which greatly increases the economic utility of the oxacylation process.

DETAILED DESCRIPTION OF THE INVENTION

[0007] The porous carriers which are suitable for preparing the catalystfor oxacylation of the present invention are alumina, silica gel,silica, active carbon, silicon carbide, diatomaceous earth, pumice andthe like, while among these, silica and alumina are preferable.

[0008] The main catalyst metal of the catalyst for oxacylation of thepresent invention is palladium; the metal content thereof, based on theweight of the carrier, is 0.1 to 5.0 weight %, preferably 0.3 to 1.5weight %. The promoter metal of the catalyst for oxacylation of thepresent invention is tin or a mixture of tin and additional metal(s)selected from the group consisting of gold, copper, cadmium, bismuth,cerium and a mixture thereof, while among these, a mixture of tin andgold is preferable; the metal content thereof, based on the weight ofthe carrier, is 0.01 to 5.0 weight %, preferably 0.02 to 1.0 weight %.The activator of the catalyst for oxacylation of the present inventionis an alkali or alkaline earth metal compound, the examples thereofbeing the hydroxides, acetates, nitrates and bicarbonates of potassium,sodium, cesium, magnesium, barium and the like, while among these,potassium salts are preferable, and potassium acetate is even morepreferable. The content thereof, based on the weight of the carrier, is1 to 15 weight %, preferably 4 to 10 weight %.

[0009] Traditionally, the preparation method of the catalyst foroxacylation was essentially comprised of the following steps: (1) acarrier was impregnated with an aqueous solution of soluble palladiumions and metal ions of the promoter; (2) the impregnated carrier wasimmersed in an alkali solution, so that the soluble palladium ions andmetal ions of the promoter were precipitated on the surface layer of thecarrier and formed into insoluble oxidative state palladium and promotermetal; (3) the treated carrier was washed with water to remove solubleions produced during the precipitation; (4) the oxidative statepalladium and promoter metal supported on the treated carrier were thenreduced to the metallic state; (5) the reduced carrier in (4) wasimpregnated with a solution of an alkali or alkaline earth metalcompound; and (6) the impregnated carrier in (5) was dried. The term“oxidative state” used herein according to the present invention means ametal in a cationic state, for example, oxidative state palladium meansPd²⁺.

[0010] The catalyst for oxacylation of the present invention is preparedmainly in accordance with the traditional method. After the oxidativestate palladium and promoter metal are supported on the surface of theporous carrier, this not-reduced yet catalyst is placed in a reactor andthe reducing step is performed under suitable reductive conditions usinggaseous or liquid reducing agents. The examples of the reducing agentsare amines, carbon monoxide, hydrogen, alkene, aldehydes and hydrazines.When gaseous reducing agents are used, it is preferable to dilute thegaseous reducing agent with inert gas (such as nitrogen gas) The amountof the reducing agent used depends on the amounts of the palladium andthe promoter metal, the equivalents used thereof usually being at least1 to 1.5 times of the equivalents required to reduce the catalyst. Ifnecessary, more reducing agent can be used. After the reducing process,the reduced catalyst is washed with deionized water until the chlorideions are completely removed and then dried. After drying, the reducedcatalyst is impregnated with an aqueous solution containing an alkali oralkaline earth metal compound. Finally, the catalyst is dried at atemperature between 80 to 150° C.

[0011] A certain amount of the above prepared catalyst for oxacylationis placed in a reacting tube with an inner diameter of 20 mm and alength of 2.0 m. Under a specific pressure at the inlet of the reactingtube, the reactant feeding gases are introduced into the tube at areacting temperature set according to the activity of the catalyst.These reactant feedings comprise propylene, nitrogen, acetic acid,oxygen and water, wherein the content of propylene is 20 to 50 volume %;the content of nitrogen is 20 to 60 volume %; the content of acetic acidis 5 to 25 volume %; the content of oxygen is 5 to 10 volume %; and thecontent of water is 0 to 15 volume %, preferably 0 to 10 volume %. Thecatalyst for oxacylation of the present invention is characterized inthat, the catalytic activity and life of the catalyst can be retainedand will not deteriorate while no water is added into the reactantcomposition, or if only a small amount of water is added in theoxacylation process.

[0012] The operation temperature of the above oxacylation process is inthe range of 100° C. to 250° C., preferably 140° C. to 200° C.; theoperation pressure is in the range of 0 to 15 kg/cm²·g, preferable 5 to10 kg/cm²·g.

[0013] The yield of allyl acetate is determined by analyzing thecomposition at the exit when the oxacylation process is carried out fora definite time.

[0014] Generally, the selection of a catalyst in the industry is basedon the catalytic activity (STY). The catalytic activity can becalculated basically according to the following formula:

[0015] The activity of a catalyst:${{STY}( {{space}\quad {time}\quad {yield}} )} = \frac{{weight}\quad {of}\quad {acetates}\quad {{produced}(g)}}{{{volume}(1)}\quad {of}\quad {catalyst} \times {sampling}\quad {{time}({hr})}}$

[0016] The selectivity of a catalyst:${{Allyl}\quad {acetate}\quad {selectivity}} = \frac{{moles}\quad {of}\quad {allyl}\quad {acetate}\quad {produced}}{\begin{matrix}{{{moles}\quad {of}\quad {allyl}\quad {acetate}\quad {produced}} +} \\{{1/3}\quad {moles}\quad {of}\quad {CO}_{2}\quad {produced}}\end{matrix}}$

[0017] It is confirmed from the evaluation of the catalytic activity inthe oxacylation process' practical application that the catalyst foroxacylation prepared in accordance with the present invention not onlyprovides higher activity of the whole oxacyltion reaction of propylene,acetic acid and oxygen, but also prolongs its own life. That is,compared to the conventional catalysts, the catalyst of the presentinvention is able to yield more allyl acetate per unit volume ofcatalyst in the reactor and per unit time, while no water or only asmall amount of water is added in the oxacylation process, and theconditions of the oxacylation reaction (such as pressure, temperature,oxygen concentration) remain constant. Thus, the energy wasted resultingfrom the traditional process by using large amounts of water can bereduced. Moreover, if the productive yield remains constant, not onlycan the reacting temperature be decreased, but also the selectivity ofthe reaction can be higher, which leads to less production of carbondioxide and less product loss during the removal of carbon dioxide.Thus, the unit raw material consumption will be lower. This isbeneficial to the industrial production of allyl acetate.

[0018] The present invention will be further, described with referenceto the following Examples and Comparative Examples, but the scope of thepresent invention is by no means limited.

EXAMPLE 1

[0019] The carrier employed in this Example was a porous carrier ofalumina/silica with an outer diameter of 5 mm and available fromSUD-CHEMIE AG. This carrier had a surface area of 100 to 120 m²/g, apore volume of 0.7 to 0.9 ml/g and a bulk density of 600 g/l. The metalcomponent-supporting catalyst was prepared according to the followingsteps:

[0020] Step 1): An aqueous Na₂PdCl₄ solution with weight of 2.2 kgcontaining 15 weight % of palladium was added into a mixture of anaqueous SnCl₂ solution with weight of 0.5 kg containing 15 weight % oftin and an aqueous HAuCl₄ solution with weight of 0.5 kg containing 30weight % of gold. The mixture was then diluted with deionized water tilltotal volume was 37.2 liters. One-hundred liters of alumina/silicacarrier was placed in an impregnating tank with rotation rate of 24turns per minute. The mixture was added into the tank rapidly.

[0021] Step 2): Hot air was passed through to dry the carrier. Thetemperature of the hot air was lower than 120° C.

[0022] Step 3): Twenty-eight weight % of NaOH solution (about 60 kg) wasadded to the dried catalyst. The originally soluble chloride statepalladium, tin and gold were transformed into insoluble hydroxide statepalladium, tin and gold.

[0023] Step 4): The impregnated catalyst carrier after drying was placedin a reducing reactor. The reducing gases were passed into the reactor,wherein the reducing gases could be diluted with other inert gases. Thehydroxide state metal catalyst was reduced into a metallic statecatalyst.

[0024] Step 5): The above catalyst was washed to remove chloride ionsuntil the catalyst was free of chloride ions.

[0025] Step 6): The catalyst carrier was dried as in step 2).

[0026] Step 7): An adequate amount of potassium acetate was added intothe dried catalyst carrier, so that each liter of the catalyst contained30 g weight of potassium acetate.

[0027] Step 8): The catalyst carrier was dried as in step 2).

[0028] After the above steps, a catalyst containing 3.3 g/l ofpalladium, 0.75 g/l of tin, 1.5 g/l of gold and 30 g/l of potassiumacetate was obtained, wherein all palladium, tin and gold were welldistributed on the surface of the carrier.

[0029] Four hundred and fifty milliliters of the catalyst thus obtainedwas charged into a reacting tube with an inner diameter of 20 mm and alength of 2.0 m. Under a pressure of 7 kg/cm² (gauge pressure) at theinlet of the reactor, the reacting gaseous mixture was introduced intothe reactor at a temperature of 140° C. The gaseous mixture wascomprised of 41 volume % of propylene, 43 volume % of nitrogen gas, 10volume % of acetic acid and 6 volume % of oxygen. When the compositionat the exit was analyzed in a definite time, the activity and theselectivity of the catalyst were calculated. The results are listed inTable 1.

[0030] When the activity and the selectivity of the catalyst wereevaluated, the crude product at the exit of the reactor was cooled withchilled water, and the composition was analyzed by Shimadzu GasChromatography. The flow rate of the gases was determined by ShinagawaDry Gas Meter.

EXAMPLE 2

[0031] The catalyst was prepared by the same method as in Example 1except that, in step 1), an aqueous Na₂PdCl₄ solution with weight of 2.2kg containing 15 weight % of palladium, an aqueous SnCl₂ solution withweight of 0.5 kg containing 15 weight % of tin and an aqueous CuCl₂solution with weight of 0.5 kg containing 15 weight % of copper wereprepared.

[0032] This catalyst was evaluated by the same method as in Example 1,and the results are listed in Table 1.

EXAMPLE 3

[0033] The catalyst was prepared by the same method as in Example 1except that, in step 1), an aqueous Na₂PdCl₄ solution with weight of 2.2kg containing 15 weight % of palladium and an aqueous SnCl₂ solutionwith weight of 0.5 kg containing 15 weight % of tin were prepared.

[0034] This catalyst was evaluated by the same method as in Example 1,and the results are listed in Table 1.

EXAMPLE 4

[0035] The catalyst was prepared exactly by the same method as inExample 1, i.e., an aqueous Na₂PdCl₄ solution with weight of 2.2 kgcontaining 15 weight % of palladium, an aqueous SnCl₂ solution withweight of 0.5 kg containing 15 weight % of tin and an aqueous HAuCl₄solution with weight of 0.5 kg containing 30 weight % of gold wereprepared.

[0036] This catalyst was evaluated by the same method as in Example 1except that, the gaseous mixture for performing oxacylation reaction wascomprised of 41 volume % of propylene, 37 volume % of nitrogen gas, 9volume % of acetic acid, 6 volume % of oxygen and 7 volume % of water,.and the results are listed in Table 1.

Comparative Example 1

[0037] The catalyst was prepared by the same method as in Example 1except that, in step 1), an aqueous Na₂PdCl₄ solution with weight of 2.2kg containing 15 weight % of palladium and an aqueous HAuCl₄ solutionwith weight of 0.5 kg containing 30 weight % of gold were prepared.

[0038] This catalyst was evaluated by the same method as in Example 4,and the results are listed in Table 1.

Comparative Example 2

[0039] The catalyst was prepared by the same method as in Example 1except that, in step 1), an aqueous Na₂PdCl₄ solution with weight of 2.2kg containing 15 weight % of palladium and an aqueous CuCl₂ solutionwith weight of 0.5 kg containing 14.6 weight % of copper were prepared.

[0040] This catalyst was evaluated by the same method as in Example 4,and the results are listed in Table 1.

Comparative Example 3

[0041] The catalyst was prepared by the same method as in Example 1except that, in step 1), an aqueous Na₂PdCl₄ solution with weight of 2.2kg containing 15 weight % of palladium and an aqueous HAuCl₄ solutionwith weight of 0.5 kg containing 30 weight % of gold were prepared.

[0042] This catalyst was evaluated by the same method as in Example 1,and the results are listed in Table 1.

Comparative Example 4

[0043] The catalyst was prepared by the same method as in Example 1except that, in step 1), an aqueous Na₂PdCl₄ solution with weight of 2.2kg containing 15 weight % of palladium and an aqueous CuCl₂ solutionwith weight of 0.5 kg containing 14.6 weight % of copper were prepared.

[0044] This catalyst was evaluated by the same method as in Example 1,and the results are listed in Table 1.

Comparative Example 5

[0045] The catalyst was prepared by the same method as in Example 1except that, in step 1), an aqueous Na₂PdCl₄ solution with weight of 2.2kg containing 15 weight % of palladium, an aqueous HAuCl₄ solution withweight of 0.5 kg containing 30 weight % of gold and an aqueous CuCl1₂solution with weight of 0.67 kg containing 15 weight % of copper wereprepared.

[0046] This catalyst was evaluated by the same method as in Example 1,and the results are listed in Table 1. TABLE 1 Relative ItemSTY-1(g/l/hr) STY-2(g/1/hr) Ratio Selectivity(%) Example 1 400 355 0.88794.8 Example 2 323 204 0.632 91.6 Example 3 350 225 0.643 92.5 Example 4410 368 0.898 95.1 Comparative 400 312 0.780 91.9 Example 1 Comparative420 353 0.840 94.5 Example 2 Comparative 375 122 0.325 92.8 Example 3Comparative 450 162 0.360 95.1 Example 4 Comparative 385 200 0.519 94.7Example 5

[0047] It is seen clearly from the above Examples and ComparativeExamples that, the activity of the traditional catalyst (see ComparativeExamples 1 to 5, wherein gold or copper was used as the catalysispromoter) deteriorates rapidly when water is not added during theoxacylation process. As to the catalyst for oxacylation produced in thepresent invention, whether only tin, or the mixture of tin/gold ortin/copper is used as the promoter, superior catalytic activitydeteriorating ratios are obtained when water is not added during theoxacylation process.

[0048] Therefore, in the presence of the catalyst produced in thisinvention, while no water is added into the reactant materials for theoxacylation process, or if only a small amount of water is added inaccordance with the requirement of the process, not only can thecatalytic activity and life of the catalyst be retained and notdeteriorate, but high catalytic activity and high selectivity will beattained. Therefore, the energy consumed and wasted resulting from theaddition of water can be avoided, and the economical effect of theoxacylation process can be greatly increased.

What is claimed is:
 1. A catalyst for oxacylation, which comprisespalladium metal as the main catalyst, tin metal or a mixture of tin andadditional metal(s) as the promoter, in combination with an alkali oralkaline earth metal compound, supported on the outer surface of aporous carrier, and being used in the process for producing allylacetate.
 2. The catalyst according to claim 1, which further comprisesmetal(s) selected from the group consisting of gold, copper, cadmium,bismuth, cerium and a mixture thereof as the additional promoter.
 3. Thecatalyst according to claim 1, wherein the content of said maincatalyst, palladium metal, based on the weight of said porous carrier,is in the range of 0.1 to 5.0 weight %.
 4. The catalyst according toclaim 3, wherein the content of said main catalyst, palladium metal,based on the weight of said porous carrier, is in the range of 0.3 to1.5 weight %.
 5. The catalyst according to claim 1, wherein the contentof said promoter, tin metal, based on the weight of said porous carrier,is in the range of 0.01 to 5.0 weight %.
 6. The catalyst according toclaim 5, wherein the content of said promoter, tin metal, based on theweight of said porous carrier, is in the range of 0.02 to 1.0 weight %.7. The catalyst according to claim 2, wherein the total content of saidpromoter, tin metal and additional metal(s), based on the weight of saidporous carrier, is in the range of 0.01 to 5.0% by weight.
 8. Thecatalyst according to claim 7, wherein the total content of saidpromoter, tin metal additional promoter metal(s), based on the weight ofsaid porous carrier, is in the range of 0.02 to 1 0% by weight
 9. Thecatalyst according to claim 1, wherein the content of said alkali oralkaline earth metal compound, based on the weight of said porouscarrier, is in the range of 1 to 15 weight %.
 10. The catalyst accordingto claim 9, wherein the content of said alkali or alkaline earth metalcompound, based on the weight of said porous carrier, is in the range of4 to 10 weight %.
 11. The catalyst according to claims 7 or 8, whereinsaid additional promoter metal is gold.
 12. The catalyst according toclaims 7 or 8, wherein said additional promoter metal is copper.
 13. Thecatalyst according to claims 7 or 8, wherein said additional promotermetal is selected from the group consisting of cadmium, bismuth andcerium.
 14. The catalyst according to claim 1, wherein said alkali oralkaline earth metal compounds are the hydroxides, acetates, nitratesand bicarbonates of potassium, sodium, cesium, magnesium and barium. 15.The catalyst according to claim 14, wherein said alkali or alkalineearth metal compounds are the hydroxide, acetate, nitrate andbicarbonate of potassium.
 16. The catalyst according to claim 1, whereinsaid porous carrier is selected from the group consisting of alumina,silica gel, silica, active carbon, silicon carbide, diatomaceous earth,pumice and a mixture thereof..
 17. The catalyst according to claim 1,wherein said process for producing allyl acetate is carried out throughthe oxacylation of propylene, acetic acid, oxygen and water in a vaporphase.
 18. The catalyst according to claim 17, wherein the content ofwater is in the range of 0 to 15 volume %, based on total amount of thereacting gases.
 19. The catalyst according to claim 18, wherein thecontent of water is in the range of 0 to 10 volume %, based on totalamount of the reacting gases.
 20. A method for preparing the catalystaccording to claim 1, which comprises: (a) impregnating a porous carrierwith a solution containing palladium and promoter metal(s) in oxidativestates, then reducing the metals from an oxidative state into metallicstate; (b) impregnating said metallic state metals-supporting carrierwith a solution of alkali or alkaline earth metal compounds, then dryingit.
 21. The method according to claim 20, wherein the reduction reactionfor reducing the metals from an oxidative state into a metallic state iscarried out in a liquid phase, and the reducing agent used is selectedfrom the group consisting of amines, aldehydes and hydrazines.
 22. Themethod according to claim 20, wherein said reduction reaction forreducing the metals from an oxidative state into a metallic state iscarried out in a vapor phase, and the reducing agent used is selectedfrom the group consisting of carbon monoxide, hydrogen and alkene.